1. Field of the Invention
This invention relates to a device for verifying the position of an endotracheal tube within the airway of an animal and the condition the lungs of an intubated animal, particularly a human.
2. Prior Art
Endotracheal intubation is essential for controlled, proactive airway management. Intubation enables the establishment and maintenance of patency while providing immediate access to the airway and the ability to regulate ventilation and deliver drugs. Further, intubation enables the health care provider to gain time for the resolution of any acute, reversible, life threatening condition by supporting vital functions that are severely compromised or at risk of failure. The disadvantage of intubation is that specialized equipment must be available, as well as a practitioner having specialized training. Since intubation is an invasive procedure, contamination, infection and related complications are an ever present danger.
Since intubation is by no means a facile procedure, a number of approaches have been developed to confirm or verify the position of the endotracheal tube within the airway of the patient. Direct visualization of the distal tip of the endotracheal tube as it passes between the vocal cords is the method most commonly used to verify correct placement of the tube. Visualization can be achieved by means of a steerable endoscope adapted for directly visualizing the cords. Endoscopic visualization is both difficult and time consuming and frequently impractical in any emergency setting. Once the patient is stabilized, radiographic verification can further confirm intubation. When endoscopic visualization equipment is not available for confirmation that the endotrachael tube is correctly positioned and radiography is impractical, auscultation of the bilateral lung fields, especially over the lateral axillary regions, may be employed. Auscultation of the properly intubated patient should produce equal breath sounds over both fields. Stethoscope auscultation over the epigastrium can be employed to ensure that the esophagus has not been intubated. The absence of air sounds over the epigastrium on ventilation indicates placement of the tube within the esophagus has not occurred. Disposable end-tidal CO.sub.2 detectors disposed in-line with the endotracheal tube airway have also been employed to detect or verify the position of the endotrachael tube within the airway of the patient. The CO.sub.2 detector comprises an element which changes color in response to the presence of CO.sub.2. Such a CO.sub.2 detector device is described, for example, in U.S. Pat. Nos. 4,879,999, 4,994,117 and 5,124,129.
Following intubation the endotracheal tube cuff is inflated. A syringe may then be used to aspirate air from the patient's lungs through the endotracheal tube. A syringe aspiration device consists of a 60 ml syringe connected to a straight ventilator circuit adapter. Aspiration of about 60 ml of air from the endotracheal tube is then attempted by retracting the plunger of the syringe. Proper intubation of the trachea is assumed if the syringe plunger can be easily retracted without resistance or rebound. If aspiration is met with resistance, or if the plunger rebounds, esophageal intubation may be assumed to have occurred. U.S. Pat. No. 5,309,903 to Long describes a syringe and means for connecting the syringe to an airway for delivering a surfactant to an intubated patient. A device similar to the arrangement shown for the Long apparatus (without the medicament) may be conveniently used for aspiration verification of proper intubation.
Many devices have been considered which utilize sound generated by a patient's breathing to either monitor the patient's breathing or to verify the correct placement of an endotracheal tube within the patient's airway. A representative sonant device is disclosed in U.S. Pat. No. 5,331,967 to Akerson which describes an acoustic resonance cavity which may be acoustically coupled to the airway of a patient. The acoustic cavity has a resonance frequency which is determined experimentally. Upon insertion of an eudotracheal tube within a patient's airway, the acoustic resonance cavity is coupled to the airway of the patient by means of a endotracheal tube adapter. The resonance frequency (or the amplitude of the acoustic resonance standing wave) within the chamber changes in a predetermined way thereby indicating acoustic connection between the airway of the patient and the acoustic cavity and verifying intubation.
U.S. Pat. No. 4,773,412 to Bloom discloses a device which may be attached to a tracheostomy tube for generating sound, which sound may be modulated by the patient for effecting speech. Other devices which employ sound for either monitoring respiration or for verifying position of an endotrachael tube following intubation are presented in U.S. Pat. Nos. 5,056,514; 4,949,716; 5,083,560, and 2,376,971. The sonant devices described in the foregoing patents each employ sound. The sound may be caused by the passage of air through the patient's airway or a synthetic audio signal or "sound" is detected by means placed within the airway. These sonant methods of monitoring air passage are in many instances adequate for verifying tube placement but are generally expensive and do not provide information regarding the condition of the lung itself. Such devices are not suitable or generally operable for determining the presence of a pneumothorax or a hemothorax.
While the foregoing devices each provide certain advantages in determining the patency of an airway or verifying the position of an endotrachael tube within a patient, none of the above prior art devices provide additional information on the condition of the lungs themselves. Further, the above intubation verification devices such as CO.sub.2 detectors and endotracheal endoscopes, are expensive and, in the case of endoscopes, require extensive training in order to be applied. The aspirator syringe method for verifying the correct position of a endotracheal tube within an airway appears to be both simple to use and accurate for verifying the position of the endotrachael tube within the airway. It would be particularly advantageous to provide an in-line device for incorporation into an adjunctive airway of an intubated patient presenting both the ability to verify the correct position of an endotracheal tube and provide additional information regarding the condition of the patients lungs.